YouTube Shorts operate with the same copyright regulations than standard YouTube video content due to their purpose as brief but entertaining segments.
The presence of an image on Pinterest does not give anyone permission to use it. Trying to use copyrighted images in your short videos outside of authorized permissions runs the risk of facing copyright infringement charges.
YouTube Shorts users should rely on royalty-free stock image websites such as Unsplash, Pexels, and Pixabay as these platforms allow commercial reuse of their images.